U.S. patent application number 09/947353 was filed with the patent office on 2002-05-02 for conductive adhesive agent, packaging structrue, and method for manufacturing the same structure.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Ishimaru, Yukihiro, Kitae, Takashi, Mitani, Tsutomu, Nishiyama, Tousaku, Takezawa, Hiroaki.
Application Number | 20020050643 09/947353 |
Document ID | / |
Family ID | 18757559 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020050643 |
Kind Code |
A1 |
Takezawa, Hiroaki ; et
al. |
May 2, 2002 |
Conductive adhesive agent, packaging structrue, and method for
manufacturing the same structure
Abstract
A conductive adhesive agent of the invention contains an elution
preventing film-forming agent 4, which becomes reactive after
electric continuity through a conductive particle 3 appeared in the
conductive adhesive agent when a binder resin 2 is being hardened,
to thereby form an elution preventing film 5 on a surface of the
conductive particle 3. By using this conductive adhesive agent, the
packaging structure is made migration resistant and sulfurization
resistant.
Inventors: |
Takezawa, Hiroaki; (Nara,
JP) ; Ishimaru, Yukihiro; (Osaka, JP) ; Kitae,
Takashi; (Osaka, JP) ; Mitani, Tsutomu;
(Hyogo, JP) ; Nishiyama, Tousaku; (Nara,
JP) |
Correspondence
Address: |
McDERMOTT, WILL & EMERY
600 13th Street, N.W.
Washington
DC
20005-3096
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
|
Family ID: |
18757559 |
Appl. No.: |
09/947353 |
Filed: |
September 7, 2001 |
Current U.S.
Class: |
257/746 ;
257/782; 257/783; 257/E21.514; 257/E23.075; 438/610 |
Current CPC
Class: |
H01L 2924/014 20130101;
H01L 2224/29111 20130101; H01R 4/04 20130101; H01L 2224/32225
20130101; H01L 2924/01006 20130101; H01L 2224/05568 20130101; H01L
2924/01078 20130101; H01L 2924/19043 20130101; H01L 2224/29444
20130101; H01L 2224/838 20130101; H01L 2924/01046 20130101; H05K
3/321 20130101; Y10T 428/2982 20150115; H01L 2924/01075 20130101;
H01L 2924/01016 20130101; H01L 2924/0665 20130101; Y02P 70/50
20151101; H01L 2224/2919 20130101; H01L 24/83 20130101; H01L
2224/29355 20130101; Y02P 70/611 20151101; H01L 2224/73204
20130101; H01L 2924/01011 20130101; H01L 2924/01047 20130101; Y10T
428/2984 20150115; H01L 2924/01033 20130101; H01L 2924/0781
20130101; C09J 9/02 20130101; H01L 24/28 20130101; H01L 2224/29439
20130101; H01L 2924/00014 20130101; H01L 2924/01013 20130101; H01L
2924/01015 20130101; H01L 2924/0132 20130101; H05K 2201/0769
20130101; H01L 2224/29339 20130101; H01L 2224/2929 20130101; H01L
2924/01023 20130101; H05K 13/0469 20130101; H01B 1/22 20130101;
H01L 2224/16225 20130101; H01L 2924/01079 20130101; H01L 2224/8319
20130101; H01L 2924/0105 20130101; H01L 2924/1579 20130101; H05K
2201/10674 20130101; H01L 2924/01327 20130101; H01L 2224/29347
20130101; H01L 2924/19041 20130101; H01L 2224/29499 20130101; H01L
2924/01029 20130101; H05K 2203/121 20130101; H01L 23/49883
20130101; H05K 2201/10636 20130101; H01L 2924/01082 20130101; H01L
2224/05573 20130101; H01L 2924/0665 20130101; H01L 2924/00
20130101; H01L 2924/0132 20130101; H01L 2924/0105 20130101; H01L
2924/01082 20130101; H01L 2224/29347 20130101; H01L 2924/00012
20130101; H01L 2924/3512 20130101; H01L 2924/00 20130101; H01L
2224/29339 20130101; H01L 2924/00014 20130101; H01L 2224/29347
20130101; H01L 2924/00014 20130101; H01L 2224/29355 20130101; H01L
2924/00014 20130101; H01L 2224/29444 20130101; H01L 2924/00014
20130101; H01L 2224/29439 20130101; H01L 2924/00014 20130101; H01L
2224/29339 20130101; H01L 2924/01046 20130101; H01L 2924/00014
20130101; H01L 2224/2929 20130101; H01L 2924/0665 20130101; H01L
2224/73204 20130101; H01L 2224/16225 20130101; H01L 2224/32225
20130101; H01L 2924/00 20130101; H01L 2924/00014 20130101; H01L
2224/05599 20130101 |
Class at
Publication: |
257/746 ;
257/783; 257/782; 438/610 |
International
Class: |
H01L 021/44; H01L
023/48 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 7, 2000 |
JP |
P2000-271245 |
Claims
What is claimed is:
1. A conductive adhesive agent comprising: a binder resin; a
conductive particle; and an elution preventing film-forming agent,
wherein said elution preventing film-forming agent becomes reactive
after electric continuity through said conductive particle appeared
in the conductive adhesive agent when said binder resin is being
hardened, to thereby form an elution preventing film on a surface
of said conductive particle.
2. The conductive adhesive agent according to claim 1, wherein a
reaction temperature of said elution preventing film-forming agent
satisfies conditions of:application temperature of conductive
adhesive agent<reaction temperature of elution preventing
film-forming agent;andreaction temperature of elution preventing
film-forming agent.ltoreq.hardening temperature of binder
resin.
3. The conductive adhesive agent according to claim 1, wherein said
elution preventing film-forming agent contains a chelating agent,
said chelating agent becoming reactive after electric continuity
through said conductive particle appeared in the conductive
adhesive agent when said binder resin is being hardened, to thereby
form an elution preventing film containing a metallic complex on a
surface of said conductive particle.
4. The conductive adhesive agent according to claim 3, wherein an
activation temperature of said chelating agent satisfies conditions
of:application temperature of conductive adhesive
agent<activation temperature of chelating agent;andactivation
temperature of chelating agent.ltoreq.hardening temperature of
binder resin.
5. The conductive adhesive agent according to claim 4, wherein said
elution preventing film-forming agent is encapsulated in a
micro-capsule, a melting temperature of said micro-capsule and an
activation temperature of a chelating agent contained in said
elution preventing film-forming agent satisfying conditions
of:application temperature of conductive adhesive agent<melting
temperature of micro-capsule;melting temperature of
micro-capsule.ltoreq.hardening temperature of binder
resin;andactivation temperature of chelating agent.ltoreq.hardening
temperature of binder resin.
6. The conductive adhesive agent according to claim 1, wherein said
elution preventing film-forming agent is made of a water-insoluble
material.
7. The conductive adhesive agent according to claim 1, wherein said
elution preventing film-forming agent is made of such a material
that is insoluble in an aqueous solution containing hydrogen
sulfide or sulfur oxide.
8. The conductive adhesive agent according to claim 3, wherein said
elution preventing film-forming agent is added, as dispersed in a
non-polar solvent, to the conductive adhesive agent.
9. A packaging structure comprising: an electrical structure; and a
conductive adhesive agent layer formed on said electrical
structure, wherein said conductive adhesive agent layer contains a
conductive particle and is coated with an elution preventing film
except at a contact point between said conductive particles and
between said conductive particle and said electrical structure.
10. The packaging structure according to claim 9, comprising
another electrical structure arranged on said electrical structure,
wherein said conductive adhesive agent layer serves to electrically
interconnect said electrical structure and said another electrical
structure.
11. The packaging structure according to claim 9, wherein said
elution preventing film is made up a material containing a metallic
complex.
12. The packaging structure according to claim 9, wherein said
elution preventing film is made up a water-insoluble material.
13. The packaging structure according to claim 9, wherein said
elution preventing film is made up a material which is insoluble in
an aqueous solution containing hydrogen sulfide or sulfur
oxide.
14. A method for manufacturing a packaging structures having an
electrical structure and a conductive adhesive agent layer formed
on an electrode of said electrical structure, comprising: a
conductive adhesive agent-forming step of preparing a conductive
adhesive agent containing a binder resin, a conductive particle,
and an elution preventing film-forming agent, a reaction
temperature of said elution preventing film-forming agent
satisfying conditions of:application temperature of conductive
adhesive agent<reaction temperature of elution preventing
film-forming agent;andreaction temperature of elution preventing
film-forming agent.ltoreq.hardening temperature of binder agent,to
then apply and form said conductive adhesive agent on said
electrode at said application temperature; an elution preventing
film-forming step of heating said conductive adhesive agent up to
said hardening temperature and permitting said elution preventing
film-forming agent to be reactive at said reaction temperature
during a course of a rise in temperature, to thereby form an
elution preventing film on said conductive particle; and a
hardening step of heating said conductive adhesive agent up to said
hardening temperature to thereby harden said binder resin.
15. The method for manufacturing a packaging structure according to
claim 14, wherein as said conductive adhesive agent, such a
material is used that contains a chelating agent and also that said
elution preventing film-forming agent is added as dispersed in a
non-polar solvent.
16. The method for manufacturing a packaging structure according to
claim 14, comprising a step of preparing said elution preventing
film-forming agent containing a chelating agent, a reaction
temperature of the chelating agent satisfying conditions
of:application temperature of conductive adhesive
agent<activation temperature of chelating agent;andactivation
temperature of chelating agent.ltoreq.hardening temperature of
binder resin,wherein during said elution preventing film-forming
step, said conductive adhesive agent is heated up to said hardening
temperature and said chelating agent is permitted to be reactive at
said activation temperature during a course of a rise in
temperature, to thereby form an elution preventing film which
contains a metallic complex on said conductive particle.
17. The method for manufacturing a packaging structure according to
claim 14, such the elution preventing film-forming agent that is
encapsulated in a micro-capsule is used, a melting temperature of
said micro-capsule and an activation temperature of a chelating
agent contained in an elution preventing film satisfying conditions
of:application temperature of conductive adhesive agent<melting
temperature of micro-capsule;melting temperature of
micro-capsule.ltoreq.hardening temperature of binder
resin;andactivation temperature of chelating agent.ltoreq.hardening
temperature of binder agent.
18. A method for manufacturing a packaging structures having an
electrical structure and a conductive adhesive agent layer formed
on an electrode of said electrical structure, comprising: a
conductive adhesive agent-forming step of preparing a conductive
adhesive agent containing a binder resin, a conductive particle,
and an elution preventing film-forming agent, a reaction
temperature of said elution preventing film-forming agent
satisfying a condition of:hardening temperature of binder
resin<reaction temperature of elution preventing film-forming
agent,to then form a layer of the conductive adhesive agent as
unhardened on said electrode; a hardening step of re-heating said
conductive adhesive agent up to said hardening temperature to
thereby harden said binder resin; and an elution preventing
film-forming step of re-heating said conductive adhesive agent up
to said reaction temperature or higher to thereby permit said
elution preventing film-forming agent to be reactive, thus forming
an elution preventing film on said conductive particle.
19. The method for manufacturing a packaging structure according to
claim 18, wherein: as said elution preventing film-forming agent,
such a material is used that contains a chelating agent which has
an activation temperature higher than a hardening temperature of
said binder resin; during said hardening step, said binder resin is
hardened through heating at a temperature lower than said
activation temperature; and during said elution preventing
film-forming step, said chelating agent is permitted to be reactive
through re-heating at a temperature not lower than said activation
temperature, thus forming an elution preventing film containing a
metallic complex on said conductive particle.
20. The method for manufacturing a packaging structure according to
claim 18, wherein such said conductive adhesive agent is used that
said elution preventing film-forming agent is added thereto as
dispersed in a non-polar solvent.
21. The method for manufacturing a packaging structure according to
claim 18, wherein such the elution preventing film-forming agent is
used that is encapsulated in a micro-capsule, a melting temperature
of said micro-capsule and an activation temperature of a chelating
agent contained in an elution preventing film satisfying conditions
of:application temperature of conductive adhesive agent<melting
temperature of micro-capsule;melting temperature of
micro-capsule.ltoreq.hardening temperature of binder
resin;andactivation temperature of chelating agent.ltoreq.hardening
temperature of binder resin.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a conductive adhesive agent used in
joining of an electronic element and a printed-circuit board in a
field of packaging of the electronic element, a packaging structure
using the conductive adhesive agent, and a method for manufacturing
the packaging structure.
[0003] 2. Description of the Related Art
[0004] Recently, high consciousness for environmental harmonies has
started to restrict use of lead contained in a solder alloy in the
field of packaging of electronic devices, thus leading to an
emergent need for establishment of technologies of joining
electronic elements using a material in which lead is not
contained.
[0005] As a lead-free packaging technology is known the one using a
lead-free solder and a conductive adhesive agent. Recently,
however, more and more attention is attracted to a conductive
adhesive agent expected to have merits such as flexibility of a
joining portion and lower packaging temperature.
[0006] A conductive adhesive agent generally has conductive
particles dispersed in a resin-based adhesive component. To package
a device, first a conductive adhesive agent is applied on a board
electrode, the device is attached thereon, and then the resin is
hardened. By this process, the joining portions are adhered to each
other by the resin and also the conductive particles come in
contact with each other as the resin shrinks, thus ensuring
continuity at the joint.
[0007] The resin of a conductive adhesive agent has a hardening
temperature of about 150.degree. C., which is very low as compared
to a melting temperature of about 240.degree. C. required for
soldering, thus qualifying that agent for use even in packaging of
such inexpensive devices that have a low heat resistance.
[0008] Also, the joining portions are adhered to each other by a
resin, thus being able to flexibly accommodating a deformation due
to heat or an external stress. This gives the conductive adhesive
agent a merit that the joining portions adhered thereby is not
liable to have cracks as compared to those adhered by solder which
is an alloy.
[0009] For the above reasons, the conductive adhesive agent is
expected as an alternative of solder.
[0010] Silver, generally used as conductive particles of a
conductive adhesive agent, has such a characteristic that it is
subject to easy ion migration or sulfurization, problem of which
must be solved to put the conductive adhesive agent to practical
use as an alternative material for solder.
[0011] First, ion migration is described as follows. A phenomenon
of ion migration is a sort of electrolytic action, by which
dielectric breakdown occurs between electrodes along the following
four steps when an electrolyte such as water is present between the
electrodes under application of voltage:
[0012] Step 1: An anode metal is eluted and ionized;
[0013] Step 2: The ionized metal migrates toward a cathode under
application of voltage;
[0014] Step 3: The metal ions which have migrated to the cathode
are precipitated; and
[0015] Step 4: Steps 1 through 3 are repeated.
[0016] Such a phenomenon of ion migration causes the metal to grow
in a tree shape between the electrodes, finally bridging the gap
between the electrodes, resulting in dielectric breakdown.
[0017] Silver used as a conductive filler of a conductive adhesive
agent is easily eluted, thus bringing about ion migration. Further,
a recent trend for further reduction in size and weight of
electronic equipment has narrowed a pitch between electrodes formed
in a semiconductor device an electronic element or on a
printed-circuit board, thus further easily causing ion migration.
Taking this into account, the problem of ion migration must be
solved indispensably to put to practical use the packaging
technology by use of a conductive adhesive agent.
[0018] There have conventionally made such three proposals that
inhibit ion migration:
[0019] Proposal 1: Alloying of conductive filler (e.g., alloying of
silver and copper or silver and palladium);
[0020] Proposal 2: Sealing of conductive adhesive agent by use of
insulating resin such as epoxy resin; and
[0021] Proposal 3: Capturing eluted metal ions and rendering them
insoluble material by addition of ion capturing agent such as ion
exchange resin or chelating agent to conductive adhesive agent
[0022] Those proposals, however, have the following disadvantages.
Proposal 1 requires a very expensive filler metal, thus increasing
a cost of the conductive adhesive agent. Proposal 2 needs to add an
extra step of sealing to thereby increase the number of required
steps or greatly expand provisions, thus increasing the
manufacturing costs. Proposal 3 causes a metal ion to be eluted
from the conductive filler to thereby deteriorate contact-ness of
the conductive filler, thus raising the connection resistance.
[0023] Thus the above-mentioned proposals have indeed an effect of
inhibiting ion migration but also have various problems and so are
difficult to put to practical use except in a special application
field.
[0024] Next, a phenomenon of sulfurization is described as follows.
Sulfurization refers to such a phenomenon that a metal reacts with
a weal acidic air containing a sulfuric content such as hydrogen
sulfide or sulfur dioxide to provide such a material with low
conductivity that is called a metal sulfide. Although sulfurization
is not know enough yet, it is considered to occur along the
following steps:
[0025] Step 1: A metal is eluted and ionized in a weak acidic
atmosphere; and
[0026] Step 2: the metal ions react with sulfur ions to generate a
metal sulfide.
[0027] As described above, a conductive filler is mainly made up of
silver but is liable to be sulfurized, so that when silver is
sulfurized, volume-specific resistance of the conductive adhesive
agent rises, which is accompanied by a rise in the connection
resistance. Few solutions for this problem have been reported so
far, so that a packaging structure using a conductive adhesive
agent cannot be applied to a product having an electronic element
which may be used in such an environment as surroundings of a hot
spring or volcano, in which hydrogen sulfide or sulfide dioxide is
present at a relatively high concentration. This greatly restrict
application fields of the packaging structure using a conductive
adhesive agent.
SUMMARY OF THE INVENTION
[0028] In view of the above, it is an object of the invention to
provide such a packaging structure using a conductive adhesive
agent that is capable of maintaining a reliability even under a
very humid condition or such a severe condition as a gaseous
atmosphere containing sulfur.
[0029] To this end, a conductive adhesive agent according to the
invention has a binder resin, a conductive particle, and an elution
preventing-film forming agent, which forming agent becomes reactive
after electrical continuity through the conductive particle is
established in this conductive adhesive agent when the binder resin
is hardened, thus forming an elution preventing film on the surface
of the conductive particle. This causes the following to occur.
[0030] When the surface of the conductive particle is coated with
the elution preventing film, the conductive particle can be
prevented from being eluted even if it is left in a hot and humid
environment or in a gas containing sulfur. Therefore, the elution
preventing film can prevent ion migration as well as the
above-mentioned first step of sulfurization. Thus, the conductive
adhesive agent according to the invention can be used to
manufacture a packaging structure not liable to encounter ion
migration and sulfurization.
[0031] When, in this case, the elution preventing film is made of
an insulating material and if it is present at a site related to
conduction (i.e., contact point between conductive particles and
that between a conductive particle and an electrode or the like),
it inhibits electrical continuity, thus leading to such a
disadvantage that raises a connection resistance of the packaging
structure.
[0032] By the conductive adhesive agent according to the invention,
on the other hand, no elution preventing film is formed on the
conductive particle until that adhesive agent is hardened, so that
only after the conductive particles come in contact with each other
in the process of hardening, the elution preventing film is formed
on the particle surface. Accordingly, the elution preventing film
is not formed at a site related to continuity, thus avoiding a rise
in the connection resistance.
[0033] If the above-mentioned requirement of the invention is not
met, on the other hand, the object of the invention cannot be
realized. That is, when an elution preventing film is formed on the
conductive particles before continuity is established, that is,
before the agent is hardened, the elution preventing film is
already present at a site related to continuity when the conductive
adhesive agent is hardened to thereby inhibit electrical
continuity, thus raising the connection resistance.
[0034] For the conductive adhesive agent according to the
invention, preferably the reactive temperature of the elution
preventing film-forming agent satisfy the following conditions:
application temperature of conductive adhesive agent<reactive
temperature of elution preventing-film forming agent;
[0035] and
reactive temperature of elution preventing film-forming
agent.ltoreq.hardening temperature of binder resin.
[0036] When these conditions are established, the following will
occur.
[0037] No elution preventing film is formed when a conductive
adhesive agent according to the invention is applied. When the
conductive adhesive agent starts to be heated to its hardening
temperature, the elution preventing film-forming agent becomes
reactive at a temperature range before the hardening to thereby
form an elution preventing film on the conductive particle. At this
point in time, the binder resin is not hardened yet so does not
inhibit the formation of the elution preventing film. Therefore,
the elution preventing film is formed uniformly everywhere on the
conductive particle surfaces except on a contact point between the
conductive particle and any other conductive substances (any other
conductive particles or electrodes). When the elution preventing
film is formed and then the conductive adhesive agent is heated up
to its hardening temperature, the binder resin is hardened to
complete connective fixation by the conductive adhesive agent.
[0038] Also, for the conductive adhesive agent according to the
invention, the elution preventing film-forming agent contains a
chelating agent, which preferably becomes reactive after electrical
continuity through the conductive particles is established in this
conductive adhesive agent when the binder resin is hardened, thus
forming an elution preventing film containing a metallic complex on
the conductive particle. Then, the following will occur.
[0039] Since the elution preventing film-forming agent contain a
chelating agent, an elution preventing film containing a very
stable material of metallic complex is formed on the conductive
particle. Accordingly, even if a connection site given by the
conductive adhesive agent is left in a hot and humid environment or
in a gas containing sulfur, the conductive particle is not
eluted.
[0040] Also, if a metallic complex, which is an insulating
material, is present at a site related to continuity (contact point
between conductive particles or between a conductive particle and
an electrode), the electrical continuity is inhibited, thus raising
the connection resistance of the packaging structure. As for a
conductive adhesive agent according to the invention, on the other
hand, no metallic complex is formed on the conductive particle
before the conductive adhesive agent is hardened, so that only
after the conductive particles come in contact with each other to
establish continuity in the hardening step, the elution preventing
film containing the metallic complex is formed on the particles.
Thus, the elution preventing film containing a metallic complex is
not formed at the site related to continuity, thus avoiding a rise
in the connection resistance.
[0041] Also, to contain a chelating agent in an elution preventing
film-forming agent for the conductive adhesive agent according to
the invention, preferably the activation temperature of the
chelating agent satisfies the following conditions:
application temperature of conductive adhesive agent<activation
temperature of chelating agent;
[0042] and
activation temperature of chelating agent.ltoreq.hardening
temperature of binder resin.
[0043] Then, the following will occur.
[0044] A chelating agent is a material which selectively reacts
with a metal to form a metallic complex, which reaction is most
liable to occur at an activation temperature of the chelating
agent. Since the activation temperature is higher than an
application temperature of the conductive adhesive agent and equal
to or lower than a hardening temperature of the binder resin, it
reacts with a metal at a temperature therebetween to thereby form
an elution preventing film containing the metallic complex on the
conductive particles. Therefore, before the conductive adhesive
agent is hardened, the chelating agent is dispersed in the
conductive adhesive agent, so that an elution preventing film is
little formed on the conductive particle. Then, in the hardening
step, the chelating agent reacts with the conductive particle to
form the elution preventing film containing a metallic complex on
the particle surfaces. This elution preventing film provides a
protecting film for the conductive particle, thus inhibiting ion
migration and sulfurization. Also, the elution preventing film is
formed after continuity is established, so that the elution
preventing film (metallic complex) is hardly formed at a site
related to continuity, thus suppressing a rise in the connection
resistance.
[0045] An activation temperature (reaction temperature) here refers
to a temperature at which a chelating agent and a metal react with
each other most frequently, generally coming near the melting
temperature. Note here that the relation between the reaction
between a chelating agent and a metal and the temperature is
nonlinear in that at the activation temperature, the reaction is
rapidly activated and at a temperature far distant from that, the
reaction occurs little.
[0046] An application temperature of the conductive adhesive agent
refers to a working temperature at which the conductive adhesive
agent is applied on a board electrode by printing or using a
dispenser in order to manufacture a packaging structure. The
application temperature generally comes near room temperature of
20-40.degree. C. or so.
[0047] If as the chelating agent is employed such a material that
has an activation temperature higher than the hardening temperature
of the binder resin (e.g., bismthyol II having a melting
temperature of 246.degree. C. as against a hardening temperature of
150.degree. C.), the chelating agent does not react with the
conductive particle even after hardening, so that no metallic
complex is formed, thus failing to obtain the effects of resisting
against ion migration and sulfurization.
[0048] Since the activation temperature is often near the melting
temperature, as the chelating agent may be used, for example, an
anthranilic acid (melting point: 145.degree. C.), thionylide
(217.degree. C.), or pyrogallol (132.degree. C.) as against such a
conductive adhesive agent that has an application temperature of
25.degree. C. and a hardening temperature of 150.degree. C.
[0049] As for the conductive adhesive agent according to the
invention, the elution preventing film-forming agent is
encapsulated in a micro-capsule, so that preferably the melting
temperature of this micro-capsule and the activation temperature of
the chelating agent contained in the elution preventing
film-forming agent satisfy the following conditions:
application temperature of conductive adhesive agent<melting
temperature of macro-capsule;
melting temperature of micro-capsule.ltoreq.hardening temperature
of binder resin;
[0050] and
activation temperature of chelating agent.ltoreq.hardening
temperature of binder resin.
[0051] When those conditions are satisfied, not only the connection
resistance of the packaging structure after hardening is inhibited
but also more chelating agents can be selected. The reasons are
explained below.
[0052] In this improvement, a chelating agent as encapsulated in a
micro-capsule is added to the conductive adhesive agent to thereby
inhibit the reaction of the unhardened chelating agent even more
securely. The reasons are described as follows.
[0053] By the configuration according to the invention, the
activation temperature of the chelating agent is higher than the
application temperature of the conductive adhesive agent, so that
the reactivity of the chelating agent is low before the binder
resin is hardened yet. However, a water content, a hardening agent
(amine, acid anhydride, or the like) a residual impurity given in
production of a binder resin (chloride, or the like), or the like
serves as a reaction accelerator, so that the chelating agent is
actually reactive even before hardening, thus forming an elution
preventing film containing a metallic complex on the conductive
particle surfaces.
[0054] As for a conductive adhesive agent according to the
invention improved as mentioned above, on the other hand, the
chelating agent is protected in a micro-capsule, so that the
chelating agent reacts little before the binder agent is hardened.
When the binder agent starts to be hardened, the micro-capsule
melts to thereby release the chelating agent, which then reacts
with the conductive particle to thereby form an elution preventing
film containing a metallic complex. Thus, by the invention improved
as mentioned above, the elution preventing film (metallic complex)
is further less formed before the binder resin is hardened, thus
securely inhibiting a rise in the connection resistance in the
conductive adhesive agent after hardening. Further, since the
activation temperature of the chelating agent may well be lower
than the application temperature of the conductive adhesive agent,
the required properties (especially activation temperature) of the
chelating agent become more lenient, thus enabling selecting more
chelating agents that much.
[0055] As for the conductive adhesive agent according to the
invention, preferably the elution preventing film-forming agent is
made up of a water-insoluble material. Then, the following will
occur.
[0056] Since the elution preventing film, once formed, does not
solve out in a hot and humid environment, the in migration
resistance is enhanced. The insoluble-ness is here defined that an
insolubility (weight soluble in 100 g of water) is less than
1.times.10.sup.-5 g.
[0057] As for a conductive adhesive agent according to the
invention, preferably the elution preventing film-forming agent is
made up of a material insoluble in a aqueous solution containing a
hydrogen sulfide or sulfur oxide. Then, the following will occur.
That is, since the elution preventing film, once formed, does not
solve out in a weak acid aqueous solution or atmosphere containing
sulfur, ion migration resistance and sulfurization resistance are
enhanced.
[0058] As for a conductive adhesive agent according to the
invention, preferably the elution preventing film-forming agent as
dispersed in a non-polar solvent is added to this conductive
adhesive agent. Then, the following will occur.
[0059] Since the non-polar solvent serves to inhibit the reaction
of the chelating agent, in the conductive adhesive agent according
to the invention improved as mentioned above, the chelating agent
is reactive little before the binder resin is hardened. When the
binder resin starts to be hardened, the chelating agent reacts with
the conductive particle to thereby form an elution preventing film
containing a metallic complex. Thus, by the invention improved as
mentioned above, the elution preventing film (metallic complex) is
formed further less before the binder resin is hardened, thus
securely inhibiting a rise in the connection resistance in the
conductive adhesive agent. Further, the activation temperature of
the chelating agent may well be lower than the application
temperature of the conductive adhesive agent, so that the required
properties (especially activation temperature) of the chelating
agent become more lenient, thus enabling selecting more chelating
agents that much.
[0060] Also, to achieve the above-mentioned object, the packaging
structure according to the invention includes an electric structure
and a conductive adhesive agent layer formed on the electric
structure in such a configuration that the conductive adhesive
agent layer contains conductive particles and is coated with an
elution preventing film except a contact point between these
conductive particles and between the conductive particle and the
electric structure.
[0061] This improves the ion migration resistance. This is because
the elution preventing film, which provides a protecting film
against ion migration, is formed on a necessary portion, that is, a
portion except those related to continuity.
[0062] A packaging structure has another electric structure
disposed on the above-mentioned one, so that these electric
structures are electrically interconnected, the conductive adhesive
agent layer has a very large effect on the connection resistance
because of an ion migration reaction, or the like. To guard against
this, the invention is applied to such a configuration so as to
have a large effect.
[0063] In a packaging structure according to the invention,
preferably the elution preventing film s made up of a material
containing a metallic complex. Then, the following will occur. That
is, since an elution preventing film containing a metallic complex,
which is very stable in property, is formed on the conductive
particle, the conductive particle does not solve out even if a site
connected by the conductive adhesive agent is left in a hot and
humid environment or in a gas containing sulfur.
[0064] Also, if a metallic complex, which is an insulating
material, is at a site related to continuity (contact point between
conductive particles or between a conductive particle and an
electrode), electrical continuity is deteriorated, thus increasing
the connection resistance of the packaging structure. A packaging
structure of the invention as improved above, on the other hand,
has no metallic complex formed at a site related to continuity,
thus avoiding to increase the connection resistance.
[0065] In the packaging structure of the invention, preferably the
elution preventing film is made up of a water-insoluble material.
Then, the elution preventing film once formed dies not solve out
even in a hot and humid environment, thus enhancing the ion
migration resistance.
[0066] In the packaging structure of the invention, preferably the
elution preventing film is made up of a material not soluble in an
aqueous solution containing hydrogen sulfide or sulfur oxide. Then,
the following will occur. That is, the elution preventing film once
formed does not solve out even in a weak acid aqueous solution or
an atmosphere containing sulfur, thus enhancing the ion migration
resistance and the sulfurization resistance.
[0067] To manufacture such a packaging structure of the invention
as mentioned above, the following two methods are available.
[0068] A first method prepares such a conductive adhesive agent
that contains a binder resin, a conductive particle, and an elution
preventing film-forming agent, a reaction temperature of which
elution preventing film-forming agent satisfies the following
conditions:
application temperature of conductive adhesive agent<reaction
temperature of elution preventing film-forming agent;
[0069] and
reaction temperature of elution preventing film-forming
agent.ltoreq.hardening temperature of binder resin,
[0070] the method comprising:
[0071] a conductive adhesive agent forming step of applying and
forming the conductive adhesive agent on the electrode at the
application temperature;
[0072] an elution preventing film-forming step of heating the
conductive adhesive agent up to the hardening temperature and also
permitting the elution preventing film-forming agent to react at
the reaction temperature before that hardening temperature is
reached to thereby form an elution preventing film on the
conductive particle; and
[0073] a hardening step of heating the conductive adhesive agent up
to the hardening temperature to harden the binder resin.
[0074] A second method prepares such a conductive adhesive agent
that contains a binder resin, a conductive particle, and an elution
preventing film-forming agent, reaction temperature of which
elution preventing film-forming agent satisfies the following
conditions:
hardening temperature of binder resin<reaction temperature of
elution preventing film-forming agent,
[0075] the method comprising:
[0076] a conductive adhesive agent forming step of forming a layer
of the conductive adhesive agent as unhardened on the
electrode;
[0077] a hardening step of heating the conductive adhesive agent up
to the hardening temperature to thereby harden the binder resin;
and
[0078] an elution preventing-film forming step of re-heating the
conductive adhesive agent to the reaction temperature or higher to
thereby permit the elution preventing film-forming agent to be
reactive, thus forming an elution preventing film on the conductive
particle.
[0079] By those manufacturing methods, the following will
occur.
[0080] That is, when a conductive adhesive agent according to the
invention, no elution preventing film is formed. Then, when the
conductive adhesive agent is heated to its hardening temperature,
at a temperature before it is hardened, the elution preventing
film-forming agent becomes reactive to thereby form an elution
preventing film on the conductive particle. At this point in time,
the binder resin is not hardened yet, thus avoiding inhibiting the
formation of the elution preventing film. Therefore, the elution
preventing film is uniformly formed everywhere on the conductive
particle surfaces except on a contact point between the conductive
particle and any other conductive materials (any other conductive
particles or electrodes, or the like). Then, when the hardening
temperature of the conductive adhesive agent is reached after the
elution preventing film is formed, the binder resin is hardened,
thus completing the connection fixation by the conductive adhesive
agent.
[0081] By the second method, a rise in the connection resistance of
the packaging structure can be inhibited further securely. The
reason is as follows.
[0082] Since the reaction temperature of the elution preventing
film-forming agent is higher than the hardening temperature of the
binder resin, before the conductive adhesive agent is hardened and
when it is being hardened, the elution preventing film-forming
agent forms no elution preventing film on the conductive particle
surfaces, thus providing good continuity. Then, the binder resin,
after being hardened, can be re-heated up to a temperature higher
than the reaction temperature of the elution preventing
film-forming agent to thereby form an elution preventing film only
at a site not related to continuity. Accordingly, the connection
resistance of the packaging structure after hardening can be
inhibited securely.
[0083] Also, preferably the first method prepares the elution
preventing film-forming agent which contains a chelating agent,
activation temperature of which satisfies the following
conditions:
application temperature of conductive adhesive agent<activation
temperature of chelating agent;
[0084] and
activation temperature of chelating agent.ltoreq.hardening
temperature of binder resin,
[0085] during the elution preventing film forming step, the
conductive adhesive agent being heated up to the hardening
temperature so that at the activation temperature before that
temperature is reached the chelating agent is made reactive to
thereby form an elution preventing film containing a metallic
complex on the conductive particle. Then, the following will
occur.
[0086] The chelating agent selectively reacts with a metal to form
a metal complex, which reaction occurs most at the activation
temperature thereof. This improved manufacturing method uses a
chelating agent and sets its activation temperature higher than the
application temperature of the conductive adhesive agent and not
higher than the hardening temperature of the binder resin.
Accordingly, the chelating agent becomes reactive at a temperature
between the application temperature of the conductive adhesive
agent and the hardening temperature of the binder resin to thereby
form an elution preventing film containing a metallic complex on
the conductive particle. Therefore, before the conductive adhesive
agent is hardened, the chelating agent is dispersed in the
conducive adhesive agent, thus scarcely forming an elution
preventing film on the conductive particle surfaces. When it starts
to be hardened, the chelating agent reacts with the conductive
particle to form an elution preventing film containing a metallic
complex on the particle surfaces. This elution preventing film
provides a protecting film for the conductive particle, thus
inhibiting ion migration and sulfurization. Also, since the elution
preventing film is formed after continuity is established, the
elution preventing film (metallic complex) is hardly formed at a
site related to continuity, thus suppressing a rise in the
connection resistance.
[0087] Preferably the second method prepares the elution preventing
film-forming agent which contains a chelating agent which has an
activation temperature higher than the hardening temperature of the
binder resin, in which:
[0088] At the hardening step, the binder resin is hardened by a
heating process at a temperature lower than the activation
temperature; and
[0089] at the elution preventing film forming step, the conductive
adhesive agent is re-heated up to a temperature not less than the
activation temperature to act with the chelating agent, thus
forming an elution preventing film containing a metallic complex on
the conductive particle. Then, it is possible to form the elution
preventing film that contains a metallic complex.
[0090] Preferably the second method prepares the elution preventing
film-forming agent that is encapsulated in a micro-capsule, so that
the melting temperature of this micro-capsule and the activation
temperature of the chelating agent containing the elution
preventing film satisfy the following conditions:
application temperature of conductive adhesive agent<melting
temperature of micro-capsule;
melting temperature of micro-capsule.ltoreq.hardening temperature
of binder resin;
[0091] and
activation temperature of chelating agent.ltoreq.hardening
temperature of binder resin,
[0092] then, a larger number of the conductive adhesive agents can
be selected optionally. The reason is as follows.
[0093] Since the melting temperature of the micro-capsule is higher
than the hardening temperature of the conductive adhesive agent,
before the binder resin is hardened or when it is being hardened,
the elution preventing film-forming agent does not form an elution
preventing film on the conductive particle surfaces, thus providing
good continuity. Then, when the binder resin is hardened and
re-heated to a temperature higher than the melting temperature of
the micro-capsule, an elution preventing film-forming is released
from the micro-capsule to thereby form an elution preventing film
only at a site not related to continuity. Accordingly, it is
possible to more securely lower the connection resistance of the
packaging structure after hardening. Also, it is not necessary to
set the reaction temperature of the elution preventing film-forming
agent at a temperature higher than the hardening temperature of the
binder resin, a larger number of the elution preventing
film-forming agents can be selected optionally.
[0094] Preferably the first and second methods uses such a
conductive adhesive agent that the elution preventing film-forming
agent is added to this conductive adhesive agent as dispersed in a
non-polar solvent. Then, the following will occur.
[0095] Since the non-polar solvent serves to inhibit the reaction
of the chelating agent, the elution preventing film-forming agent
added to the conductive adhesive agent as dispersed in the
non-polar solvent causes the chelating agent to be reactive little
before the binder resin is hardened. Then, when the binder resin
starts to be hardened, the chelating agent reacts with the
conductive particle to form an elution preventing film containing a
metallic complex. Accordingly, the elution preventing film
(metallic complex) is formed further less before the binder resin
is hardened, thus securely inhibiting a rise in the connection
resistance in the conductive adhesive agent after being hardened.
Further, since the activation temperature of the chelating agent
may well be not higher than the application temperature of the
conductive adhesive agent, the required properties (especially
activation temperature) of the chelating agent come lenient, thus
increasing the number of the chelating agents that can be used.
[0096] In the above-mentioned invention, the following materials
can be used.
[0097] As the binder resin, almost all resins relatively easily
available can be used. For example, as the thermo-hardening resin
can be used epoxy resin, phenol resin, urea resin, melamine resin,
furan resin, unsaturated-resin polyester resin, di-allyl phthalate
resin, silicon resin, or the like. Also, as the thermo-hardening
resin can be used vinyl chloride resin, vinylidene chloride resin,
polystyrene resin, ionomer, methyl-penten resin, poly-allomer,
fluorine resin, a poly-imide, poly-amide, poly-amide-imide,
poly-carbonate, modified poly-phenylene oxide, poly-phenylene
sulfide.
[0098] The micro-capsule may be made of such relatively easily
available thermo-hardening resins as vinyl chloride resin,
vinylidene chloride resin, polystyrene resin, ionomer,
methyl-pentene resin, poly-allomer, fluorine resin, poly-amide,
poly-imide, poly-amide-imide, poly-carbonate, modified
poly-phenylene oxide, poly-phenylene sulfide, or the like. Note
here that the melting temperature of the micro-capsule can be
adjusted arbitrarily by adjusting the molar weight of the resin or
the film thickness of the micro-capsule.
[0099] If the above-mentioned variety of requirements of the
conductive adhesive agent and the packaging structure set by the
invention are not satisfied, no object of the invention can be
realized. The reason is described as follows.
[0100] If the melting point of the micro-capsule is not higher than
the application temperature of the conductive adhesive agent, the
micro-capsule melts before hardening, so that the elution
preventing film-forming agent is released, thus forming an elution
preventing film on the conductive particle surfaces, thus
increasing the connection resistance of the packaging structure
after hardening.
[0101] If the melting point of the micro-capsule is higher than the
hardening temperature, the elution preventing film-forming agent
does not react with the conductive particle even after hardening to
thereby form no elution preventing film, thus failing to obtain the
ion migration resistance nor the sulfurization resistance.
[0102] Also, if as the elution preventing film-forming agent added
to the conductive adhesive agent is employed such an agent that has
as its main component a chelating agent having an activation
temperature higher than the hardening temperature (for example,
bismthyol II having a melting point of 246.degree. C. as against a
hardening temperature of 150.degree. C.), the elution preventing
film-forming agent does not react with the conductive particle even
after hardening to thereby form no elution preventing film, thus
failing to obtain the ion migration resistance nor the
sulfurization resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0103] The above and other objects of the invention will be more
apparent from the following description taken in conjunction with
the accompanying drawings and described in the accompanying claim.
Many advantages of the invention not described in the specification
may be apparent to those skilled in the art.
[0104] FIG. 1 are expanded diagrams for showing an important part
of a conductive adhesive agent according to a first embodiment of
the invention, of which FIG. 1 shows a state before hardening, FIG.
1B shows a state where continuity appears during hardening, and
FIG. 1C shows a state after hardening;
[0105] FIG. 2 is a cross-sectional view for showing a flip chip
packaging structure according to a second embodiment of the
invention;
[0106] FIG. 3 is a plan view for showing the chip element packaging
structure according to a third embodiment of the invention;
[0107] FIG. 4 is a plan view for showing a printed-circuit board
used in evaluation of ion migration resistance; and
[0108] FIG. 5 is a plan view for showing a testing sample used in
evaluation of sulfurization resistance.
DETAILED DESCRIPTION OF THE INVENTION
[0109] The following will describe embodiments of the invention
with reference to the drawings.
[0110] First Preferred Embodiment
[0111] This embodiment implements the invention in a conductive
adhesive agent. FIGS. 1A-1C are expanded diagrams for showing an
important part of the conductive adhesive agent according to this
embodiment. FIG. 1A shows a state before being hardened, FIG. 1B
shows a state where continuity appeared during its hardening, and
FIG. 1C shows a state where it is hardened completely. In FIG. 1A,
the conductive adhesive agent 1 comprises a liquid-state binder
resin 2 in which are mixed and dispersed a conductive particle 3
and an elution preventing film-forming agent 4 having a chelating
agent as its main component. In a hardening step shown in FIG. 1B,
the conductive particles 3 are in contact with each other and the
elution preventing film-forming agent particles are still dispersed
in the binder resin 2 which is half-hardened. In FIG. 1C, the
conductive particles 3 are in contact with each other with portions
thereof not in contact mutually being coated with an elution
preventing film 5 having a metallic complex as its main component
in the binder resin 2 which is half-hardened.
[0112] As the binder resin 2 the following may be used. That is, as
the thermo-hardening resin may be used epoxy resin, phenol resin,
urea resin, melanin resin, furan resin, unsaturated-resin polyester
resin, diallyl phthalate resin, silicon resin, or the like. Also,
as the thermo-plastic resin may be used vinyl chloride resin,
vinylydene chloride resin, polystylene resin, ionomer,
methyl-penten resin, poly-allomer, fluorine resin, poly-amide,
poly-imide, poly-amide-imide, poly-carbonate, modified
poly-phenylene oxide, poly-phenylene sulfide, or the like.
[0113] As the chelating agent constituting the main component of
the elution preventing film-forming agent 4, for example,
anthranilic acid (melting point: 143.degree. C..apprxeq.activation
temperature) or pyrogallol (melting point: 132.degree.
C..apprxeq.activation temperature) may be used if the conductive
adhesive agent has an application temperature of 25.degree. C. and
a hardening temperature of 150.degree. C.
[0114] Also, as the conductive particle 3, Ag, an alloy of Cu,
Cu--, or Ag or an alloy of Cu, Ni, or Ag--Pd coated with Au or Ag
may be used. Of these, Ag is preferable taking into account the
volume inherent resistance or the material cost.
[0115] Second Preferred Embodiment
[0116] This embodiment implements the invention in a flip-chip
packaging structure for a semiconductor device. As shown in FIG. 2,
this packaging structure comprises a printed-circuit board 6, which
is one example of the electrical structure, and a semiconductor
device 7, which is another example of the electrical structure. The
semiconductor device 7 is comprised of an IC substrate 8 and a bump
electrode 9 formed on the surface of the IC substrate 8. The
printed-circuit board 6 has an I/O terminal electrode 10 on its
surface. The I/O terminal electrode 10 has formed thereon a
conductive adhesive agent layer 1A made of the conductive adhesive
agent 1 described in the first embodiment, through which layer 1A
are electrically interconnected the I/O terminal electrode 10 and
the bump electrode 9. Further, a sealing resin 11 is provided to
fill the gap between the semiconductor device 7 and the
printed-circuit board 6, thus constituting the flip-chip packaging
structure.
[0117] Third Preferred Embodiment
[0118] This embodiment implements the invention in a packaging
structure for a chip element. As shown in FIG. 3, this packaging
structure has such a configuration that on the surface thereof are
mounted an electrode 13 of a printed-circuit board 12, which is one
example of the electrical structure, a chip resistor 14, which is
another example of the electrical structure, a chip coil 15, and a
chip capacitor 16. The electrode 13 has formed thereon the
conductive adhesive agent layer 1A made of the conductive adhesive
agent 1 described in the first embodiment, through layer 1A are
electrically interconnected the electrode 13 and these chip
elements 14, 15, and 16.
[0119] Examples of the above-mentioned embodiments are explained
below.
[0120] First, practical examples (conductive adhesive agent) of the
first embodiment are described below.
PRACTICAL EXAMPLE 1
[0121] By this practical example, the conductive adhesive agent 1
described in the first embodiment features the elution preventing
film-forming agent 4, which is a liquid agent which has as its main
component an anthranilic acid (melting point: 143.degree.
C..apprxeq.activation temperature), which is the chelating agent.
The anthranilic acid reacts with an Ag particle to form an
anthranilic acid Ag, which is a metallic complex, on the particle
surfaces. Note here that the activation temperature (reaction
temperature) of the anthranilic acid, the application temperature
of the conductive adhesive agent, the hardening temperature of the
conductive adhesive agent satisfy the following relations:
application temperature (32.degree. C.) of conductive adhesive
agent<activation temperature (143.degree. C.) of anthranilic
acid;
[0122] and
activation temperature (143.degree. C.) of anthranilic
acid.ltoreq.hardening temperature (150.degree. C.) of binder
resin.
[0123] Therefore, the elution preventing film-forming agent 4
containing the anthranilic acid reacts with the conductive particle
3 when the binder resin 2 is hardening, to form the elution
preventing film 5 containing the metallic complex. Also, the
anthranilic acid Ag, which is a metallic complex formed by this
reaction, may be assumed to be non-ionizing and insoluble in water
and an aqueous solution containing a hydrogen sulfide or sulfur
oxide.
[0124] Next, a method of manufacturing the conductive adhesive
agent according to this practical example is described as follow.
The liquid binder resin 2 (7 weight-%) made of thermo-hardening
epoxy resin, the conductive particle 3 (92 weight-%) made of Ag,
the elution preventing film-forming agent 4 (2 weight-%) having
anthranilic acid as its main component, an addition agent, a
dispersion agent, an adherence improver (2 weight-%), and the like
are dispersed and mixed using a three-piece roll to provide the
conductive adhesive agent 1 of this practical example.
PRACTICAL EXAMPLE 2
[0125] As a feature of this practical example, in the configuration
of the conductive adhesive agent described in practical example 1,
the elution preventing film-forming agent is the elution preventing
film-forming agent 4 which has, as its main component,
1-nitroso-2-naphthol (melting point: 110.degree. C.) which serves
as the chelating agent employed in place of anthranilic acid. The
other conditions are totally the same as those of practical example
1, that is, the configuration conditions of the conductive adhesive
agent material, the manufacturing method, the application
temperature, the hardening temperature, or the like.
[0126] The 1-nitroso-2-naphthol has an activation temperature
(reaction temperature.apprxeq.melting point) of (110.degree. C. or
so) and reacts with the conductive particle 3 when the binder resin
2 is being hardened, to form a metallic complex, that is, the
elution preventing film 4 which has 1-nitroso-2-naphthol Ag as its
main component. The 1-nitroso-2-naphthol Ag is an ionizing material
and very easily solved in water and easily absorbs water and an
aqueous solution which contains hydrogen sulfide or sulfur
oxide.
PRACTICAL EXAMPLE 3
[0127] As a feature of this practical example, in the configuration
of the conductive adhesive agent described in practical example 1,
the elution preventing film-forming agent 4 is given as something
obtained by encapsulating a chemical agent having anthranilic acid
as its main component in a micro-capsule with hexamethylene
phthalamide resin (melting temperature: 87.degree. C.). The other
conditions are totally the same as those of practical example 1,
that is, the configuration conditions of the conductive adhesive
agent material, the manufacturing method, the application
temperature, the hardening temperature, or the like. The softening
temperature of the micro-capsule, the application temperature of
the conductive adhesive agent, and the hardening temperature of the
conductive adhesive agent satisfy the following relations:
application temperature of conductive adhesive agent (32.degree.
C.)<melting temperature of micro-capsule (87.degree. C.);
melting temperature of micro-capsule (87.degree.
C.).ltoreq.hardening temperature of binder resin (150.degree.
C.);
[0128] and
activation temperature of anthranilic acid (143.degree.
C.).ltoreq.hardening temperature of binder resin (150.degree.
C.).
[0129] Therefore, when the binder resin 2 is being hardened, the
micro-capsule melts to release the elution preventing film-forming
agent 4 from itself, which agent 4 (=anthranilic acid) in turn
reacts with the conductive particle 3 to form the elution
preventing film 5 containing a metallic complex.
[0130] Note here that the elution preventing film-forming agent 4
is encapsulated in the micro-capsule by a publicly known interface
polymerization reaction method. The manufacturing method is
detailed as follows. Into an aqueous solution of 7.5 ml in which
0.4M of 1,6-hexamethylene di-amine and 0.45M of sodium carbonate
are solved is added an equivalent amount of water, so that a 15-ml
volume of this solvent is subsequently is added to a 75-ml volume
of a mixture solution of chloroform and cyclo-hexan (volume ration:
1:4) containing a 5% of anthranilic acid, which is then well
stirred and emulsified to provide water/oil type emulsion. After
five minutes of emulsification, phthaloyl dichloride is added to
the emulsion while stirring it. This causes the condensation
polymerization reaction to occur between phthaloyl di-chloride and
di-amine on the surface of a water droplet in the emulsion, to
produce hexamethylene phthalamide. The above steps causes the
elution preventing film-forming agent 4 to be encapsulated in a
micro-capsule.
PRACTICAL EXAMPLE 4
[0131] As a feature of this practical example, in the configuration
of the conductive adhesive agent described in practical example 1,
the elution preventing film-forming agent 4 is given as something
that has, as its main component, bismthyol II (melting point:
246.degree. C..apprxeq.activation temperature) in place of
anthranilic acid and also the method includes a step of re-heating
at a temperature higher than the activation temperature of the
elution preventing film-forming agent 4 after the conductive
adhesive agent 1 is hardened. The other conditions are totally the
same as those of practical example 1, that is, the configuration
conditions of the conductive adhesive agent material, the
manufacturing method, the application temperature, the hardening
temperature, or the like. The activation temperature of the elution
preventing film-forming agent (chelating agent), the hardening
temperature of the conductive adhesive agent 1, and the re-heating
temperature satisfy the following relations:
hardening temperature of binder resin (150.degree.
C.).ltoreq.activation temperature of bismthyol II (246.degree.
C.);
[0132] and
activation temperature of bismthyol II (246.degree.
C.)<re-heating temperature (250.degree. C.).
PRACTICAL EXAMPLE 5
[0133] As a feature of this practical example, in the configuration
of the conductive adhesive agent described in practical example 4,
as the chelating agent constituting the main component of the
elution preventing film-forming agent 4, anthranilic acid
(activation temperature: 143.degree. C.) is employed in place of
bismthyol II and also this elution preventing film-forming agent 4
is encapsulated in a micro-capsule with hexamethylene phthalamide
resin (melting temperature: 162.degree. C.). The other conditions
are totally the same as those of practical example 1, that is, the
configuration conditions of the conductive adhesive agent material,
the manufacturing method, the application temperature, the
hardening temperature, or the like. The activation temperature
(reaction temperature) of the elution preventing film-forming agent
4, the hardening temperature of the conductive adhesive agent 1,
the re-heating temperature, and the melting temperature of the
capsule satisfy the following relations:
hardening temperature of binder resin (150.degree. C.)<melting
temperature of micro-capsule (162.degree. C.);
melting temperature of micro-capsule (162.degree. C.)<re-heating
temperature (170.degree. C.);
[0134] and
activation temperature of hexamethylene phthalamide (143.degree.
C.)<re-heating temperature (170.degree. C.).
[0135] Therefore, the elution preventing film-forming agent 4 stays
non-reactive during the hardening step but reacts with the
conductive particle at the re-heating step to form the elution
preventing film 5 containing a metallic complex.
[0136] Corresponding to the above-mentioned practical examples 1-5,
the conductive adhesive agent is prepared according to the
following comparison examples 1-3.
Comparison Example 1
[0137] The conductive adhesive agent according to this comparison
example has such a configuration that he elution preventing
film-forming agent 4 is removed from the configuration of a prior
art conductive adhesive agent, that is, the conductive adhesive
agent 1 of practical example 1, with the content ratio of the
conductive particle 3 being the same as practical example 1. That
is, this conductive adhesive agent 1 comprises the liquid binder 2
(6 weight-%) made of a thermo-hardening epoxy resin, the conductive
particle 3 (92 weight-%) made of Ag, and addition agents (2
weight-%) such as a hardening agent, dispersion agent, or adherence
improver, which are dispersed and mixed using a three-piece
roll.
Comparison Example 2
[0138] This conductive adhesive agent according to this comparison
example has such a configuration that the conductive adhesive agent
of practical example 1 contains, as the chelating agent, bismthyol
II (melting point: 246.degree. C..apprxeq.activation temperature)
having an activation temperature higher than the hardening
temperature of the conductive adhesive agent. The activation
temperature of the chelating agent, the application temperature of
the conductive adhesive agent, and the hardening temperature of the
conductive adhesive agent satisfy the following conditions:
application temperature of the conductive adhesive agent
(32.degree. C.)<hardening temperature of binder resin
(150.degree. C.);
[0139] and
hardening temperature of binder resin (150.degree.
C.)<activation temperature of bismthyol II (246.degree. C.).
[0140] Therefore, in this comparison example 2, the chelating agent
stays non-reactive at the hardening step for the binder resin, so
that the elution preventing film 5 containing a metallic complex is
not formed on the surfaces of the conductive particle 3.
Comparison Example 3
[0141] This conductive adhesive agent has such a configuration that
the conductive adhesive agent of practical example 1 contains, as
the chelating agent, toluene-3,4-dithiol (melting point: 31.degree.
C..apprxeq.activation temperature) which has an activation
temperature lower than the application temperature of the binder
resin 2. The activation temperature of the chelating agent, the
application temperature of the conductive adhesive agent, and the
hardening temperature of the conductive adhesive agent satisfy the
following conditions:
activation temperature of toluene-3,4-dithiol (31.degree.
C.)<application temperature of conductive adhesive agent
(32.degree. C.);
[0142] and
application temperature of conductive adhesive agent (32.degree.
C)<hardening temperature of binder agent (150.degree. C.).
[0143] Therefore, the chelating agent in an unhardened state reacts
with the conductive particle to form an elution preventing film
containing a metallic complex on the particle surfaces.
[0144] The conductive adhesive agent thus prepared according to
practical examples 1-5 and comparison examples 1-3 is used to form
a conductive adhesive agent layer for evaluation and measurement as
follows.
[0145] Evaluation of Ion Migration Resistance (Water Droplet Drop
Test)
[0146] A water droplet drop test is a method for evaluating the ion
migration resistance of a material rapidly and simply. The testing
method is detailed as follows. As shown in FIG. 4, as a testing
sample, comb-shaped conductive adhesive agent layers 18 and 19 are
formed on a ceramic-made testing substrate 17 by a screen printing
method. The conductive adhesive agent layers 18 and 19 are
separated from each other by a predetermined inter-electrode
distance (400 .mu.m) and arranged as opposed so that their tips may
alternate, with no current generally flowing therebetween.
[0147] Deionized water is dropped on thus formed conductive
adhesive agent layers 18 and 19 and a DC voltage (1 V) is applied
therebetween. Then, a time lapse is measured which elapses from a
time point of short-circuiting between the conductive adhesive
agent layers 18 and 19 up to a time point that a current starts to
flow, so that the ion migration resistance is measured on the basis
of that short-circuiting time lapse.
[0148] Evaluation of Sulfurization Resistance
[0149] As shown in FIG. 5, on a glass epoxy-made testing board 20,
a gold-plated electrode 21 is formed, on which is in turn formed a
conductive adhesive agent layer 1A made of the conductive adhesive
agent 1 by the screen printing method. On the conductive adhesive
agent layer 1A is then mounted a 3216-size 0-.OMEGA. resistor
(terminal plating: SnPb solder) 22 using a mount packaging machine.
Next, to harden the conductive adhesive agent layer 1A, it is
heated in an oven at 150.degree. C. for 30 minutes. Thus prepared
samples are measured for the initial connection resistance and then
left in an enclosed bath filled with hydrogen sulfide to thereby
measure a change in the connection resistance, thus evaluating the
sulfurization resistance. The testing conditions includes a
temperature of 40.degree. C., a humidity of 90%, a concentration of
the hydrogen sulfide of 3 ppm, and a testing time of 96 hours.
[0150] The results of the above-mentioned evaluation and
measurements are summarized in Table 1. Note here that the
conductive adhesive agent was applied in all the tests at an
application temperature (working temperature) of 32.degree. C.
1 TABLE 1 Chelating Sulfurization agent Capsule Metallic Migration
test results (Activation (Softening complex Re- Test Initial value
-> temperature) temperature) Solubility heating results value
after 96 H Embodiment Anthranilic None Insoluble None 965 sec 42
m.OMEGA. -> 42 m.OMEGA. 1 acid (143.degree. C.) Embodiment
1-nitroso- None Soluble None 842 sec 42 m.OMEGA. -> 45 m.OMEGA.
2 2-naphthaol (110.degree. C.) Embodiment Anthranilic HMFA
Insoluble None 970 sec 38 m.OMEGA. -> 38 m.OMEGA. 3 acid
(87.degree. C.) (143.degree. C.) Embodiment Bismthyol None
Insoluble 250.degree. C. 960 sec 35 m.OMEGA. -> 35 m.OMEGA. 4 II
5 min (246.degree. C.) Embodiment Anthranilic HMFA Insoluble
170.degree. C. 963 sec 35 m.OMEGA. -> 35 m.OMEGA. 5 acid
(162.degree. C.) 5 min (143.degree. C.) Comparison None None --
None 86 sec 35 m.OMEGA. -> 98 m.OMEGA. example 1 Comparison
Toluene- None Insoluble None 964 sec 126 m.OMEGA. -> 126
m.OMEGA. example 2 3,4-dithiol (31.degree. C.) Comparison Bismthyol
None Insoluble None 86 sec 36 m.OMEGA. -> 101 m.OMEGA. example 3
II (246.degree. C.) *HMFA: Hexamethylene phthalamide
[0151] Comparison of the conductive adhesive agents according to
practical examples 1-5 to comparison examples 1-3 shows the
following. That is, the evaluation of the ion migration resistance
indicates that the time lapse up to a point in time when a current
starts to flow was prolonged as compared to the case of using the
prior art conductive adhesive agent (comparison example 1) so it is
confirmed that the ion migration resistance was improved. Also, the
evaluation of the sulfurization indicates that a ratio of a change
in the connection resistance as measured before and after testing
was reduced as compared to comparison example 1 so it is confirmed
that the sulfurization resistance was improved.
[0152] Further, the comparison assures the following. That is,
comparison between practical example 1 where the metallic complex
constituting the main component of the elution preventing film 5
formed on the surfaces of the conductive particle 3 is insoluble in
water and an aqueous solution containing hydrogen sulfide or sulfur
oxide and practical example 2 where it is soluble them reveals that
practical example 1 came up with better ion migration resistance
and sulfurization resistance. This is considered because the
elution preventing film (metallic complex) formed, if it is
insoluble in water and an aqueous solution containing hydrogen
sulfide or sulfur oxide, is less subject to flake-off even when the
water or the aqueous solution containing sulfur is condensed on the
surfaces of the film.
[0153] Comparison between practical example 1 where the elution
preventing film-forming agent 4 (chelating agent) is added as it is
into the conductive adhesive agent 1 and practical example 3 where
it is added as encapsulated in a micro-capsule reveals that
practical example 3 came up with a lower initial connection
resistance. This is considered because when it is encapsulated in
the micro-capsule, the reaction of the elution preventing
film-forming agent 4 as unhardened can be more surely inhibited,
thus reducing the amount of the insulating elution preventing film
5 (metallic complex) which exists at a contact point between the
conductive particles 3 or the conductive particle 3 and the
electrode 13 or 21. Note here that although in practical example 3
the elution preventing film-forming agent 4 which has, as its main
component, anthranilic acid having an activation temperature higher
than the application temperature of the conductive adhesive agent 1
is encapsulated in a micro-capsule, the elution preventing
film-forming agent 4 can have, as its main component, such a
chelating agent that has an activation temperature lower than the
application temperature of the conductive adhesive agent 1, thus
extending the range of selectable elution preventing film-forming
agents (chelating agents) as compared to practical example 1.
[0154] Comparison between practical example 1 using the elution
preventing film-forming agent 4 having as its main component such a
chelating agent that becomes reactive at a hardening step of the
conductive adhesive agent 1 and practical example 4 using the
elution preventing film-forming agent 4 having as its main
component such a chelating agent that does not become reactive at
the hardening step so that the elution preventing film-forming
agent 4 may become reactive at the re-heating step after the
hardening step reveals that practical example 4 came up with a
lower initial connection resistance, almost equal to an initial
value obtained in the case (comparison example 1) where the prior
art conductive adhesive agent was used. This is considered because
that in practical example 4 the elution preventing film 4 becomes
reactive in formation after continuity appeared at the hardening
step, so that the elution preventing film 5 is formed little at a
continuity site.
[0155] As may be clear from practical example 5, when the elution
preventing film-forming agent 4 is encapsulated in a micro-capsule
in practical example 4, almost the same ion migration resistance
and sulfurization resistance can be obtained and, in addition to
that, the range of selectable elution preventing film-forming agent
4 is extended. This is because practical example 4 needs to use the
elution preventing film-forming agent 4 containing such a chelating
agent that has an activation temperature (reaction temperature)
higher than the hardening temperature, whereas practical example 5
can accept any activation temperature of the elution preventing
film-forming agent 4 as far as the melting temperature of the
micro-capsule is set higher than the hardening temperature of the
binder resin 2. For example, it is possible to use even such an
elution preventing film-forming agent 4 that has an activation
temperature lower than the application temperature of the
conductive adhesive agent 1.
[0156] Note here that if the conditions described in practical
examples 1-5 are not satisfied, the intended effects cannot be
obtained. The evidence is given in comparison examples 2 and 3.
[0157] Comparison example 2 indicates a case of using such an
elution preventing film-forming agent 4 that has, as its main
component, a chelating agent having an activation temperature lower
than the application temperature of the conductive adhesive agent
1. This case came up with an extremely high initial connection
resistance as compared to practical example 1, that is, a case
where the activation temperature is higher than the application
temperature. This is because that the elution preventing
film-forming agent 4 reacts as unhardened with the conductive
particle 3 to form the elution preventing film 5 (metallic
complex), so that an insulating elution preventing film 5 (metallic
complex) is present at a site related to continuity of the
conductive particles 3, thus increasing the contact resistance.
[0158] Also, comparison example 3 indicates a case of using such an
elution preventing film-forming agent 4 that has, as its main
component, a chelating agent having an activation temperature
higher than the hardening temperature of the conductive adhesive
agent 1. Comparison example 3 came up with such a result that the
ion migration resistance and the sulfurization resistance were
extremely inferior as compared to practical example 1, that is, a
case where the activation temperature of the chelating agent is
lower than the hardening temperature. This is because that the
elution preventing film-forming agent 4 is not reactive at the
hardening step for the conductive adhesive agent 1 (binder resin
2), thus failing to form the elution preventing film (metallic
complex) 4 on the surfaces of the conductive particle 3.
[0159] Next, the practical examples of the second preferred
embodiment (flip chip packaging structure for semiconductor device)
are described as follows.
PRACTICAL EXAMPLE 6
[0160] As a feature of this practical example, as the elution
preventing film-forming agent 4, the conductive adhesive agent of
practical example 1 using, as its man component, anthranilic acid,
which is a chelating agent (except that a thermoplastic epoxy resin
is used as the liquid binder resin 2), is used to flip-chip package
the semiconductor device 7 on the printed-circuit board 6. That is,
the conductive adhesive agent 1 described in practical example 1 is
transferred by a publicly known method onto the bump electrode 9 of
the semiconductor device 7. Then, with thus transferred conductive
adhesive agent 1 as aligned with the I/O terminal electrode 10 of
the printed-circuit board 6, the semiconductor device 7 is
flip-chip packaged on the printed-circuit board 6. Then, after the
conductive adhesive agent 1 is hardened, an electrical test is
performed to then harden the sealing resin 11 made of
thermo-hardening epoxy resin supplied between the printed-circuit
board 6 and the semiconductor device 7 which came up with good
results of testing, to thereby seal the related jointed site, thus
providing a flip chip packaging structure.
PRACTICAL EXAMPLE 7
[0161] As a feature of this practical example, as the elution
preventing film-forming agent 4, the conductive adhesive agent 1 of
practical example 2 having, as its main component,
1-nitroso-2-naphthol, which is a chelating agent, is used to
constitute the flip chip packaging structure. The configuration and
the manufacturing method of the flip chip packaging structure are
totally the same as those of practical example 6 except the
conductive adhesive agent employed.
PRACTICAL EXAMPLE 8
[0162] As a feature of this practical example, as the elution
preventing film-forming agent 4, such a material that has, as its
main component, anthranilic acid, which is a chelating agent, is
used and, at the same time, the conductive adhesive agent 1 of
practical example 3 for encapsulating this elution preventing
film-forming agent 4 in a micro-capsule with a hexamethylene
phtalamide resin is used to constitute the flip chip packaging
structure. The configuration and the manufacturing method of the
flip chip packaging structure are totally the same as those of
practical example 6 except the conductive adhesive agent 1
employed.
PRACTICAL EXAMPLE 9
[0163] As a feature of this practical example, as the elution
preventing film-forming agent 4, the conductive adhesive agent 1
having, as its main component, the bismthyol II, which is a
chelating agent, is hardened and then undergoes re-heating
according to the method of practical example 4, to constitute the
flip chip packaging structure. The configuration and the
manufacturing method of the flip chip packaging structure are
totally the same as those of practical example 6 except the
conductive adhesive agent employed.
PRACTICAL EXAMPLE 10
[0164] As a feature of this practical example, as the elution
preventing film-forming agent 4, such a material that has, as its
main component, anthranilic acid, which is a chelating agent, and
also that encapsulates this elution preventing film-forming agent 4
in a micro-capsule with a hexamethylene phtalamide resin is used
and then undergoes re-heating after the conductive adhesive agent 1
is hardened according to the method of practical example 5, to form
the flip chip packaging structure. The configuration and the
manufacturing method of the flip chip packaging structure are
totally the same as those of practical example 6 except the
conductive adhesive agent 1 employed.
Comparison Examples 4-6
[0165] Corresponding to the above-mentioned practical examples
6-10, the flip chip packaging structures of comparison examples 4-6
are prepared.
[0166] These flip chip packaging structures are supposed to use the
conductive adhesive agent of comparison example 1 and also have the
same packaging constructions as those of practical examples
6-10.
[0167] Thus prepared flip chip packaging structures of practical
examples 6-10 and comparison examples 4-6 are evaluated in terms of
reliability according to the following method.
[0168] That is, as flowing an in-actual-use current (10 mA) through
these flip chip packaging structures, the method measured them for
a change in the connection resistance in a hot and humid
environment (temperature: 85.degree. C., humidity: 85%, testing
time 1000 hours), to perform evaluation and measurement of the ion
migration resistance. Likewise, as flowing an in-actual-use current
(10 mA) through them, the method measured them for a change in the
connection resistance in a hydrogen sulfide atmosphere
(temperature: 40.degree. C., humidity: 90%, concentration of
hydrogen sulfide: 3 ppm, testing time: 96 hours), to perform
evaluation and measurement of the sulfurization resistance. The
results are shown in Table 2.
2 TABLE 2 Migration Sulfurization Chelating results test results
agent Capsule Metallic Initial value Initial value (Activation
(Softening complex Re- -> value after -> value temperature)
temperature) Solubility heating 1000 H after 96 H Embodiment
Anthranilic None Insoluble None 21 m.OMEGA. -> 21 m.OMEGA. 21
m.OMEGA. -> 21 m.OMEGA. 6 acid (143.degree. C.) Embodiment
1-nitroso- None Soluble None 21 m.OMEGA. -> 27 m.OMEGA. 21
m.OMEGA. -> 23 m.OMEGA. 7 2-naphthaol (110.degree. C.)
Embodiment Anthranilic HMFA Insoluble None 19 m.OMEGA. -> 19
m.OMEGA. 19 m.OMEGA. -> 19 m.OMEGA. 8 acid (87.degree. C.)
(143.degree. C.) Embodiment Bismthyol None Insoluble 250.degree. C.
17 m.OMEGA. -> 17 m.OMEGA. 17 m.OMEGA. -> 17 m.OMEGA. 9 II 5
min (246.degree. C.) Embodiment Anthranilic HMFA Insoluble
170.degree. C. 17 m.OMEGA. -> 17 m.OMEGA. 17 m.OMEGA. -> 17
m.OMEGA. 10 acid (162.degree. C.) 5 min (143.degree. C.) Comparison
None None -- None 17 m.OMEGA. -> OPEN 17 m.OMEGA. -> 50
m.OMEGA. example 4 Comparison Toluene- None Insoluble None 1.5
.OMEGA. -> 1.5 .OMEGA. 1.5 .OMEGA. -> 1.5 .OMEGA. example 5
3,4-dithiol (31.degree. C.) Comparison Bismthyol None Insoluble
None 1.8 m.OMEGA. -> 121.sup. 18 m.OMEGA. -> 53 m.OMEGA.
example 6 II m.OMEGA. (246.degree. C.) *HMFA: Hexamethylene
phthalamide
[0169] Comparison of the flip chip packaging structures according
to practical examples 6-10 to comparison examples 4-6 shows the
following. That is, the evaluation of the ion migration resistance
indicates that the time lapse up to a point in time when a current
starts to flow was prolonged as compared to the case of using the
prior art conductive adhesive agent (comparison example 4) so it is
confirmed that the ion migration resistance was improved. Also, the
evaluation of the sulfurization indicates that a ratio of a change
in the connection resistance as measured before and after testing
was reduced as compared to comparison example 4 so it is confirmed
that the sulfurization resistance was improved.
[0170] Further, the comparison assures the following. That is,
comparison between practical example 6 where the elution preventing
film 5 formed on the surfaces of the conductive particle 3 is
insoluble in water and an aqueous solution containing hydrogen
sulfide or sulfur oxide and comparison example 7 where it is
soluble in them reveals that practical example 6 came up with
better ion migration resistance and sulfurization resistance. This
is considered because the elution preventing film 5 formed, if it
is insoluble in water and an aqueous solution containing hydrogen
sulfide or sulfur oxide, is less subject to flake-off even when the
water or the aqueous solution containing sulfur is condensed on the
surfaces of the film.
[0171] Also, comparison between practical example 6 where the
elution preventing film-forming agent 4 is added as it is into the
conductive adhesive agent 1 and practical example 8 where it is
added as encapsulated in a micro-capsule reveals that practical
example 8 came up with a lower initial connection resistance. This
is considered because when it is encapsulated in the micro-capsule,
the reaction of the elution preventing film-forming agent 4 as
unhardened can be more surely inhibited, thus reducing the amount
of the insulating elution preventing film 5 which exists at a
contact point between the conductive particles 3 or the conductive
particle 3 and the electrode 13 or 21. Note here that in practical
example 8 the elution preventing film-forming agent 4 which has, as
its main component, anthranilic acid having a reaction temperature
(activation temperature) higher than the application temperature of
the conductive adhesive agent 1 is encapsulated in a micro-capsule.
In this practical example 8, however, it is possible to use even
such an elution preventing film-forming agent 4 that has, as its
main component, a chelating agent exhibiting a reaction temperature
(activation temperature) lower than the application temperature of
the conductive adhesive agent 1, thus extending the range of
selectable elution preventing film-forming agents (chelating
agents) as compared to practical example 6.
[0172] Further, comparison between practical example 6 using the
elution preventing film-forming agent 4 which becomes reactive at
the hardening step of the conductive adhesive agent 1 and practical
example 9 using the elution preventing film-forming agent 4 which
is not reactive at that hardening step so that reaction may occur
at the re-heating step reveals that practical example 9 came up
with a lower initial connection resistance, almost equal to an
initial value obtained in the case (comparison example 1) where the
prior art conductive adhesive agent was used. This is considered
because that in practical example 9 the elution preventing film 4
becomes reactive after continuity appeared at the hardening step,
so that the elution preventing film 5 is formed little at a
continuity site.
[0173] Also, as may be clear from practical example 10, when the
elution preventing film-forming agent 4 is encapsulated in a
micro-capsule in the configuration of practical example 9, almost
the same ion migration resistance and sulfurization resistance can
be obtained and, in addition to that, the range of selectable
elution preventing film-forming agent 4 is extended. This is
because practical example 9 needs to use the elution preventing
film-forming agent 4 exhibiting an activation temperature higher
than the hardening temperature, whereas practical example 10 can
accept any reaction temperature (activation temperature) of the
elution preventing film-forming agent 4 as far as the melting
temperature of the micro-capsule is set higher than the hardening
temperature of the binder resin 2. Although such an elution
preventing film-forming agent 4 that has, as its main component,
anthranilic acid having an activation temperature higher than the
application temperature of the conductive adhesive agent 1 has been
used in practical example 10, this practical example 10 can use
such an agent 4 that has, as its main component, a chelating agent
exhibiting an activation temperature lower than the application
temperature of the conductive adhesive agent 1.
[0174] Note here that if the conditions described in practical
examples 6-10 are not satisfied, the intended effects cannot be
obtained. The evidence is given in comparison examples 5 and 6.
[0175] Comparison example 5 indicates a case of using such an
elution preventing film-forming agent 4 that has, as its main
component, a chelating agent having an activation temperature lower
than the application temperature of the conductive adhesive agent
1. This case came up with an extremely high initial connection
resistance as compared to practical example 6, that is, a case
where the reaction temperature (activation temperature) of the
elution preventing film is higher than the application temperature
of the conductive adhesive agent 1. This is because that the
elution preventing film-forming agent 4 reacts as unhardened with
the conductive particle 3 to form an elution preventing film
(metallic complex), so that an insulating elution preventing film
(metallic complex) is present at a site related to continuity of
the conductive particles 3, thus increasing the contact
resistance.
[0176] Also, comparison example 6 indicates a case where the
elution preventing film-forming agent 4 has a reaction temperature
(activation temperature) higher than the hardening temperature of
the conductive adhesive agent 1. This case came up with such a
result that the ion migration resistance and the sulfurization
resistance were extremely inferior as compared to practical example
5, that is, a case where the reaction temperature (activation
temperature) of the elution preventing film-forming agent 4 is
lower than the hardening temperature of the conductive adhesive
agent 1. This is because that the elution preventing film-forming
agent 4 is not reactive at the hardening step for the conductive
adhesive agent 1 (binder resin 2), thus failing to form the elution
preventing film 5 on the surfaces of the conductive particle 3.
[0177] Thus, practical examples 6-10 (flip chip packaging
structure) also provide almost the same effects as those by
practical examples 1-5 (conductive adhesive agent).
[0178] Although practical examples 6-10 have used the conductive
adhesive agent 1 having a thermoplastic epoxy resin to provide
electric connection between the semiconductor device and the
printed-circuit board, a thermo-hardening epoxy resin may be used
instead to have almost the same effects like in the case of the
first embodiment.
[0179] The following will describe the practical examples of the
third embodiment (chip-element packaging structure).
PRACTICAL EXAMPLE 11
[0180] This practical example provides a chip-element packaging
structure which is made using a conductive adhesive agent of
practical example 1. Note here that practical example 1 has used
such an elution preventing film-forming agent 4 that has, as its
main component, an anthranilic acid, which is an chelating agent.
This chip-element packaging structure comprises a printed-circuit
board (30.times.60 mm, thickness: 1.6 mm) 12 made of glass epoxy,
on which the electrode 13 is formed by Au plating and then the
0-.OMEGA. chip resistor (3216 size, SnPb plating) 14, the chip coil
(diameter: 8 mm.phi., height: 4 mm) 15, and the chip capacitor
(3215 size, SnPb plating) 16 are packaged.
[0181] This chip-element packaging structure is made as follows.
First, the conductive adhesive agent 1 is screen-printed on the
electrode 13 of the printed-circuit board 12. Then, the chip
elements 14, 15, and 16 are mounted on the electrode 13 using an
existing element mounting machine and undergo heating in an oven at
150.degree. C. for 30 minutes, thus hardening the conductive
adhesive agent 1.
PRACTICAL EXAMPLE 12
[0182] As a feature of this practical example, the chip-element
packaging structure is made up of the conductive adhesive agent 1
of practical example 2 using such an elution preventing
film-forming agent 4 that has, as its main component,
1-nitroso-2-naphthol, which is a chelating agent. The configuration
and the manufacturing method of the chip-element packaging
structure are totally the same as those of practical example 11
except the conductive adhesive agent employed.
PRACTICAL EXAMPLE 13
[0183] As a feature of this practical example, as the elution
preventing film-forming agent 4, the conductive adhesive agent,
which is a chelating agent, is used and, the conductive adhesive
agent of practical example 3 for encapsulation into a micro-capsule
by use of hexamethylene phtalamide is used to make the chip-element
packaging structure. The configuration and the manufacturing method
of the chip-element packaging structure are totally the same as
those of practical example 11 except the conductive adhesive agent
1 employed.
PRACTICAL EXAMPLE 14
[0184] As a feature of this practical example, as the elution
preventing film-forming agent 4, the conductive adhesive agent 1
having, as its main component, the bismthyol II, which is a
chelating agent, is used and then undergoes re-heating after the
conductive adhesive agent is hardened according to the method of
practical example 3, to constitute the chip-element packaging
structure. The configuration and the manufacturing method of the
chip-element packaging structure are totally the same as those of
practical example 11 except the conductive adhesive agent 1
employed.
PRACTICAL EXAMPLE 15
[0185] As a feature of this practical example, as the elution
preventing film-forming agent 4, such a material that has, as its
main component, anthranilic acid, which is a chelating agent, and
also that encapsulates this elution preventing film-forming agent 4
in a micro-capsule with a hexamethylene phtalamide resin is used
and then undergoes re-heating after the conductive adhesive agent 1
is hardened according to the method of practical example 5, to form
the flip chip packaging structure. The configuration and the
manufacturing method of the flip chip packaging structure are
totally the same as those of practical example 11 except the
conductive adhesive agent 1 employed.
Comparison Examples 7-9
[0186] Corresponding to the above-mentioned practical examples
11-15, the chip-element packaging structures of comparison examples
7-9 are prepared.
[0187] These chip-element packaging structures are supposed to use
the conductive adhesive agent of comparison example 1 and also have
the same packaging constructions as those of practical examples
11-15.
[0188] Thus prepared chip-element packaging structures of practical
examples 11-15 and comparison examples 7-9 are evaluated in terms
of reliability according to the following method.
[0189] As flowing an in-actual-use current (10 mA) through these
chip-element packaging structures, the method measured them for a
change in the connection resistance in a hot and humid environment
(temperature: 85.degree. C., humidity: 85%, testing time 10000
hours), to perform evaluation and measurement of the ion migration
resistance. Likewise, as flowing an in-actual-use current (10 mA)
through them, the method measured them for a change in the
connection resistance in a hydrogen sulfide atmosphere
(temperature: 40.degree. C., humidity: 90%, concentration of
hydrogen sulfide: 3 ppm, testing time: 96 hours), to perform
evaluation and measurement of the sulfurization resistance. The
results are shown in Table 3.
3 TABLE 3 Migration Sulfurization Chelating results test results
agent Capsule Metallic Initial value Initial value (Activation
(Softening complex Re- -> value after -> value temperature)
temperature) Solubility heating 1000 H after 96 H Embodiment
Anthranilic None Insoluble None 30 m.OMEGA. -> 30 m.OMEGA. 30
m.OMEGA. -> 30 m.OMEGA. 11 acid (143.degree. C.) Embodiment
1-nitroso- None Soluble None 31 m.OMEGA. -> 35 m.OMEGA. 31
m.OMEGA. -> 38 m.OMEGA. 12 2-naphthaol (110.degree. C.)
Embodiment Anthranilic HMFA Insoluble None 27 m.OMEGA. -> 27
m.OMEGA. 27 m.OMEGA. -> 27 m.OMEGA. 13 acid (87.degree. C.)
(143.degree. C.) Embodiment Bismthyol None Insoluble 250.degree. C.
24 m.OMEGA. -> 24 m.OMEGA. 24 m.OMEGA. -> 24 m.OMEGA. 14 II 5
min (246.degree. C.) Embodiment Anthranilic HMFA Insoluble
170.degree. C. 24 m.OMEGA. -> 24 m.OMEGA. 24 m.OMEGA. -> 24
m.OMEGA. 15 acid (162.degree. C.) 5 min (143.degree. C.) Comparison
None None -- None 24 m.OMEGA. -> OPEN 24 m.OMEGA. -> 59
m.OMEGA. example 7 Comparison Toluene- None Insoluble None 2.7
.OMEGA. -> 2.7 .OMEGA. 2.7 .OMEGA. -> 2.7 .OMEGA. example 8
3,4-dithiol (31.degree. C.) Comparison Bismthyol None Insoluble
None 25 m.OMEGA. -> 163.sup. 25 m.OMEGA. -> 67 m.OMEGA.
example 9 II m.OMEGA. (246.degree. C.) *HMFA: Hexamethylene
phthalamide
[0190] Comparison of the chip-element packaging structures
according to practical examples 11-15 to comparison examples 7-9
shows the following. That is, the evaluation of the ion migration
resistance indicates that the time lapse up to a point in time when
a current starts to flow was prolonged as compared to the case of
using the prior art conductive adhesive agent (comparison example
7) so it is confirmed that the ion migration resistance was
improved. Also, the evaluation of the sulfurization indicates that
a ratio of a change in the connection resistance as measured before
and after testing was reduced as compared to comparison example 7
so it is confirmed that the sulfurization resistance was
improved.
[0191] Further, the comparison assures the following. That is,
comparison between practical example 11 where the metallic complex
formed on the surfaces of the conductive particle is insoluble in
water and an aqueous solution containing hydrogen sulfide or sulfur
oxide and comparison example 12 where it is soluble in them reveals
that practical example 11 came up with better ion migration
resistance and sulfurization resistance. This is considered because
the elution preventing film 5 formed, if it is insoluble in water
and an aqueous solution containing hydrogen sulfide or sulfur
oxide, is less subject to flake-off even when the water or the
aqueous solution containing sulfur is condensed on the surfaces of
the film.
[0192] Also, comparison between practical example 11 where the
elution preventing film-forming agent 4 is added as it is into the
conductive adhesive agent 1 and practical example 13 where it is
added as encapsulated in a micro-capsule reveals that practical
example 13 came up with a lower initial connection resistance. This
is considered because when it is encapsulated in the micro-capsule,
the reaction of the elution preventing film-forming agent 4 as
unhardened can be more surely inhibited, thus reducing the amount
of the insulating elution preventing film (metallic complex) which
exists at a contact point between the conductive particles 3 or the
conductive particle 3 and the electrode 21. Note here that although
practical example 13 has shown the case where the elution
preventing film-forming agent 4 which has, as its main component,
anthranilic acid, which is a chelating agent having an activation
temperature higher than the application temperature of the
conductive adhesive agent 1, is encapsulated in a micro-capsule, it
is possible to use even such an elution preventing film-forming
agent 4 that has, as its main component, a chelating agent
exhibiting an activation temperature lower than the application
temperature of the conductive adhesive agent 1, thus extending the
range of selectable elution preventing film-forming agents 4
(chelating agents) as compared to practical example 11.
[0193] Further, comparison between practical example 13 using the
elution preventing film-forming agent 4 which becomes reactive at
the hardening step of the conductive adhesive agent 1 and practical
example 14 using the elution preventing film-forming agent 4 which
is not reactive at that hardening step so that reaction may occur
at the re-heating step reveals that practical example 14 came up
with a lower initial connection resistance, almost equal to an
initial value obtained in the case (comparison example 7) where the
prior art conductive adhesive agent was used. This is considered
because that in practical example 14 the elution preventing film 4
becomes reactive after continuity appeared at the hardening step,
so that the elution preventing film 5 is formed little at a
continuity site.
[0194] Also, as may be clear from practical example 15, when the
elution preventing film-forming agent 4 is encapsulated in a
micro-capsule in the configuration of practical example 14, almost
the same ion migration resistance and sulfurization resistance can
be obtained and, in addition to that, the range of selectable
elution preventing film-forming agent 4 (chelating agent) is
extended. This is because practical example 14 needs to use the
elution preventing film-forming agent 4 which has, as its main
component, a chelating agent exhibiting an activation temperature
higher than the hardening temperature, whereas practical example 15
can accept any activation temperature of the elution preventing
film-forming agent 4 (chelating agent) as far as the melting
temperature of the micro-capsule is set higher than the hardening
temperature of the binder resin 2. Although such an elution
preventing film-forming agent 4 that has, as its main component,
anthranilic acid having an activation temperature higher than the
application temperature of the conductive adhesive agent 1 has been
used in practical example 15, this practical example can use such
an agent 4 that has, as its main component, a chelating agent
exhibiting an activation temperature lower than the application
temperature of the conductive adhesive agent 1.
[0195] Note here that if the conditions described in practical
examples 11-15 are not satisfied, the intended effects cannot be
obtained. The evidence is given in comparison examples 8 and 9.
[0196] Comparison example 8 indicates a case of using such an
elution preventing film-forming agent 4 that a reaction temperature
(activation temperature) lower than the application temperature of
the conductive adhesive agent 1. This case came up with an
extremely high initial connection resistance as compared to
practical example 11, that is, a case where the above-mentioned
reaction temperature (activation temperature) is higher than the
application temperature of the conductive adhesive agent 1. This is
because that the elution preventing film-forming agent 4 reacts as
unhardened with the conductive particle 3 to form the elution
preventing film 5, so that an insulating elution preventing film 5
(metallic complex) is present at a site related to continuity of
the conductive particles 3, thus increasing the contact
resistance.
[0197] Also, comparison example 9 indicates a case where the
elution preventing film-forming agent 4 has a reaction temperature
(activation temperature) higher than the hardening temperature of
the conductive adhesive agent 1. This case came up with such a
result that the ion migration resistance and the sulfurization
resistance were extremely inferior as compared to practical example
11, that is, a case where the reaction temperature (activation
temperature) is lower than the hardening temperature of the binder
resin 2. This is because that the elution preventing film-forming
agent 4 is not reactive at the hardening step of the conductive
adhesive agent 1, thus failing to form the elution preventing film
5 on the surfaces of the conductive particle 3.
[0198] Thus, practical examples 11-15 (chip-element packaging
structure) also provide almost the same effects as those by
practical examples 1-5 (conductive adhesive agent) and practical
examples 6-10 (flip chip packaging structure).
[0199] Although practical examples 11-15 have shown only the
packaging structures for chip elements as an example of the
packaging structure for the elements, of course they can be used to
package all the other elements including, for example, such package
elements as a QFP (Quad Flat Package), CSP (Chip Scale Package), or
BGA (Ball Grid Array), such chip or lead elements as an
electrolytic capacitor, diode, or switch, and IC bare packages.
Also, the elution preventing film-forming agent and the like are
not limited in application to the above-mentioned embodiments as
far as the requirements are satisfied.
[0200] In any of the above-mentioned practical examples, the
elution preventing film-forming agent 4 can be added, as dispersed
in a non-polar solvent, to a conductive adhesive agent. Then, the
following will occur.
[0201] Since a non-polar solvent serves to inhibit the reaction of
a chelating agent, if the elution preventing film-forming agent 4
is added, as dispersed in the non-polar solvent, to a conductive
adhesive agent, the chelating agent is little reactive in a state
where the binder resin is not hardened yet. Then, when the binder
resin is being hardened, the chelating agent reacts with a
conductive particle to form an elution preventing film containing a
metallic complex. Accordingly, the elution preventing film 5 is
formed further less when the binder resin is not hardened yet, thus
surely inhibiting a rise in the connection resistance in the
conductive adhesive agent 1 after hardening. Further, since the
activation temperature of the chelating agent may be lower than the
application temperature of the conductive adhesive agent, the
required properties (especially, activation temperature) of the
chelating agent become lenient, thus extending the range of
selectable chelating agents that much.
[0202] As is clear from the above-mentioned embodiments and
practical examples, by the invention such a packaging structure
that is excellent in the ion migration resistance and the
sulfurization resistance as compared to a prior art one can be
obtained.
[0203] Also, the invention, if applied to such a packaging
structure as a flip chip or chip-element packaging structure,
improves the insulation reliability to thereby enable reducing the
connection distance such as an inter-electrode distance, thus
saving on a space for the packaging structure.
[0204] Further, since the invention improves the reliability
against sulfurization, it can be applied to such a product that may
be used in a gas atmosphere containing a lot of sulfur, such as in
the neighboring area of hot springs or in the vicinity of
volcanoes, thus greatly possibly extending the application
fields.
[0205] Although the invention has been described with respect to
its most preferred embodiments, their combination and the
arrangement can be variously changed without departing from the
spirit and the scope of the accompanying claims.
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